Matrix Isolated Free Radicals:  Chemistry and Physics Below 3 K


Professor David M. Lee

Department of Physics and Laboratory of Atomic & Solid Physics

Cornell University






          In this lecture, studies of atomic hydrogen, atomic deuterium and atomic nitrogen embedded in solid inert molecular matrices will be discussed.  At first glance it would appear that chemical reactions would not occur in these systems.  In fact, such reactions can and do proceed via quantum mechanical tunneling.  For example, a deuterium atom can tunnel through an inert lattice.  If it encounters a hydrogen molecule in the lattice, a free hydrogen atom is released and an HD molecule is formed.   Such a reaction is called an exchange tunneling reaction.  Hydrogen atoms can move through a molecular hydrogen lattice via a series of successive reactions.  Recently we have observed some tantalizing evidence that Bose-Einstein condensation may be occurring in an ensemble of hydrogen atoms embedded in solid molecular hydrogen.  Spin pair radicals have also been observed in samples of atomic nitrogen embedded in solid molecular nitrogen.  A video tape will be shown of colorful explosive recombination events where nitrogen atoms recombine to form diatomic nitrogen molecules.